Mathematical Physics

Abstract: We build a new estimate for the normalized eigenfunctions of the operator
$-\partial_{xx}+\mathcal V(x)$ based on the oscillatory integrals and Langer's
turning point method, where $\mathcal V(x)\sim |x|^{2\ell}$ at infinity with
$\ell>1$. From it and an improved reducibility theorem we show that the
equation \[\textstyle
{\rm i}\partial_t \psi =-\partial_x^2 \psi+\mathcal V(x) \psi+\epsilon
\langle x\rangle^{\mu} W(\nu x,\omega t)\psi,\quad \psi=\psi(t,x),~x\in\mathbb
R, ~\mu<\min\left\{\ell-\frac23,\frac{\sqrt{4\ell^2-2\ell+1}-1}2\right\},\] can
be reduced in $L^2(\mathbb R)$ to an autonomous system for most values of the
frequency vector $\omega$ and $\nu$, where $W(\varphi, \phi)$ is a smooth map
from $ \mathbb T^d\times \mathbb T^n$ to $\mathbb R$ and odd in $\varphi$.